Coating composition with solar properties

ABSTRACT

A coating composition is disclosed. The coating composition includes an infrared reflective layer; a primer layer over the infrared reflective layer; a dielectric layer over the primer layer; and an absorbing layer, wherein the absorbing layer can be either under the infrared reflective layer or over the dielectric layer.

FIELD OF THE INVENTION

The present invention relates to a coating composition that can beapplied on substrates to provide a coated substrate that exhibits lowvisible light transmittance and low visible light reflectance from atleast one side of the substrate.

BACKGROUND OF THE INVENTION

Privacy glass, defined as glass which has a low visible transmittance(i.e., less than or equal to 50%), can be used in a variety ofapplications such as automotive applications and architecturalapplications. There are generally no limitations regarding where privacyglass can be incorporated in a building. In some automotiveapplications, privacy glass can only be incorporated in the rear windowand rear sidelights due to the regulations imposed in the United Statesand some other countries.

Typically, a substrate, either coated or uncoated, that will be used asprivacy glass is highly absorbtive or is highly reflective in thevisible region of the electromagnetic spectrum. For example, the privacyglass can comprise an uncoated, tinted glass substrate with goodabsorptive properties in the visible region. In the alternative, theprivacy glass can comprise a coated, clear glass substrate with highreflectivity in the visible region. In another alternative embodiment,the privacy glass can comprise a laminated product formed, for example,with a tinted substrate and a clear, coated substrate.

The present invention provides a novel coating that can be used totransform a glass substrate into privacy glass. The coated substrate ofthe present invention exhibits reduced visible reflectance, which isaesthetically desirable, while providing solar reflection in theinfrared region on at least one side of the substrate which reduces theheat load.

SUMMARY OF THE INVENTION

In a non-limiting embodiment, the present invention is a coatingcomposition comprising: an infrared reflective layer; a primer layerover the infrared reflective layer; a dielectric layer over the primerlayer; and an absorbing layer, wherein the absorbing layer can be eitherunder the infrared reflective layer or over the dielectric layer.

In another non-limiting embodiment, the present invention is a coatedsubstrate comprising: a substrate; an infrared reflective layer over thesubstrate; a primer layer over the infrared reflective layer; adielectric layer over the primer layer; and an absorbing layer, whereinthe absorbing layer can be either under the infrared reflective layer orover the dielectric layer.

In yet another non-limiting embodiment, the present invention is amethod for forming a coating comprising: depositing an infraredreflecting layer; depositing a primer layer over the infrared reflectivelayer; depositing a dielectric layer over the primer layer; anddepositing an absorbing layer, wherein the absorbing layer can bedeposited either under the infrared reflective layer or over thedielectric layer, and wherein when the coating is deposited on a 0.16inch thick clear glass substrate, the substrate exhibits an Lta of lessthan or equal to 50% and an L* of equal to or less than 52 from at leastone side of the substrate

DESCRIPTION OF THE INVENTION

All numbers expressing dimensions, physical characteristics, quantitiesof ingredients, reaction conditions, and the like used in thespecification and claims are to be understood as being modified in allinstances by the term “about”. Accordingly, unless indicated to thecontrary, the numerical values set forth in the following specificationand claims may vary depending upon the desired properties sought to beobtained by the present invention. At the very least, and not as anattempt to limit the application of the doctrine of equivalents to thescope of the claims, each numerical parameter should at least beconstrued in light of the number of reported significant digits and byapplying ordinary rounding techniques. Moreover, all ranges disclosedherein are to be understood to encompass any and all subranges subsumedtherein. For example, a stated range of “1 to 10” should be consideredto include any and all subranges between (and inclusive of) the minimumvalue of 1 and the maximum value of 10; that is, all subranges beginningwith a minimum value of 1 or more and ending with a maximum value of 10or less, e.g., 1.0 to 7.8, 3.0 to 4.5, and 6.3 to 10.0.

As used herein, the terms “on”, “applied on/over”, “formed on/over”,“deposited on/over”, “overlay” and “provided on/over” mean formed,overlay, deposited, or provided on but not necessarily in contact withthe surface. For example, a coating layer “formed over” a substrate doesnot preclude the presence of one or more other coating layers of thesame or different composition located between the formed coating layerand the substrate. For instance, the substrate can include aconventional coating such as those known in the art for coatingsubstrates, such as glass or ceramic.

In a non-limiting embodiment, the present invention is a coatingcomposition comprising one or more infrared reflecting layers, one ormore primer layers, one or more dielectric layers, and one or moreabsorbing layers capable of absorbing at least a portion of energy inthe visible region of the electromagnetic spectrum.

According to the present invention, the one or more infrared reflectivelayers can comprise gold, copper, silver and mixtures thereof as is wellknown in the art.

According to the present invention, the infrared reflective layer(s) canbe deposited using any of the standard techniques such as chemical vapordeposition (“CVD”), spray pyrolysis, magnetron sputtering vapordeposition (“MSVD”) which are well known in the art. If the coatinglayer is made up of more than one discrete film, the describeddeposition techniques can be used to deposit some or all of the filmsthat make up the total coating layer.

Suitable CVD methods of deposition are described in the followingreferences, which are hereby incorporated by reference: U.S. Pat. Nos.4,853,257; 4,971,843; 5,536,718; 5,464,657; 5,599,387; and 5,948,131.

Suitable spray pyrolysis methods of deposition are described in thefollowing References, which are hereby incorporated by reference: U.S.Pat. Nos. 4,719,126; 4,719,127; 4,111,150; and 3,660,061.

Suitable MSVD methods of deposition are described in the followingreferences, which are hereby incorporated by reference: U.S. Pat. Nos.4,379,040; 4,861,669; and 4,900,633.

The infrared reflective layer(s) can have any thickness. In anon-limiting embodiment, the thickness of each infrared reflective layercan range from 50 Å to 200 Å, for example, from 70 Å to 160 Å or from 90Å to 130 Å.

According to the present invention, one or more primer layers can beover the infrared reflective layer(s). The primer layer acts as asacrificial layer that protects the infrared reflective layer fromoxidizing conditions. By acting as a sacrificial layer, the primer layeroxidizes instead of the infrared reflective layer. In a non-limitingembodiment of the invention, the primer layer comprises a materialselected from titanium, zirconium, and mixtures thereof.

The primer layer(s) can be deposited using any of the standardtechniques discussed above in relation to the infrared reflective layer.

The primer layer(s) can have any thickness. In a non-limitingembodiment, the thickness of each primer layer can range from 1 Å to 60Å, for example, from 10 Å to 35 Å or from 12 Å to 25 Å.

According to the present invention, one or more dielectric layers can beover the primer layer(s). The dielectric layer can be made up of asingle film or a plurality of films. Suitable materials for thedielectric layer include, but are not limited to, metal oxides, oxidesof metal alloys, nitrides, oxynitrides, or mixtures thereof. Examples ofsuitable metal oxides include, but are not limited to, oxides oftitanium, hafnium, zirconium, niobium, zinc, bismuth, lead, indium, tin,and mixtures thereof. Additionally, the dielectric layer can compriseoxides of metal alloys or metal mixtures, such as, but not limited to,oxides containing zinc and tin, oxides of indium-tin alloys, siliconnitrides, silicon aluminum nitrides, oxynitrides, or aluminum nitrides.

In a non-limiting embodiment of the invention, the dielectric layercomprises a metal alloy oxide film comprising a zinc/tin alloy oxide.The zinc/tin alloy can comprise zinc and tin in proportions ranging from10 wt. % to 90 wt. % zinc and 90 wt. % to 10 wt. % tin.

In a non-limiting embodiment of the invention, the dielectric layercomprises zinc stannate. The term “zinc stannate” refers to acomposition of ZnXSn1-XO2-X (Formula 1) where x is greater than 0 butless than 1. For example, if x=2/3, the zinc stannate formed would berepresented by Zn2/3Sn1/3O4/3, which is commonly described as “Zn2SnO4”.A zinc stannate containing coating has one or more of films according toFormula 1 in a predominant amount, i.e., zinc stannate is present in anamount greater than any other material in the coating.

In a non-limiting embodiment of the invention, the dielectric layer ismade up of a material that is doped, for example, with antimony, nickel,boron, manganese, indium, etc. For example, the dielectric layer cancomprise tin oxide doped with antimony or indium, silicon oxide dopedwith nickel or boron, zinc oxide doped with tin, etc.

If more than one dielectric layer is present in an embodiment of thepresent invention, the dielectric layers in the coating can have thesame composition or a different compositions.

The dielectric layer(s) of the present invention can be deposited usingstandard techniques as discussed above in relation to the infraredreflective layer.

According to the present invention, the dielectric layer(s) can have anythickness. In a non-limiting embodiment, the thickness of eachdielectric layer can range from 200 Å to 900 Å, for example, from 250 Åto 800 Å.

According to the present invention, one or more absorbing layers can beover the dielectric layer. The absorbing layer is capable of absorbingat least a portion of energy in the visible region of theelectromagnetic spectrum to, among other things, reduce the luminoustransmittance of the coated substrate. In a non-limiting embodiment ofthe invention, the absorbing layer comprises an alloy and/or mixture of(a) a metal having an index of refraction at 500 nm equal to or lessthan 1.0 and (b) a material that has a ΔG°_(f) of greater to or equalthan −100 at 1,000° K. Examples of materials that have a ΔG°_(f) ofgreater to or equal than −100 at 1,000° K. include, but are not limitedto, tin, indium, copper, zinc as well as mixtures thereof. Anon-limiting example of the absorbing layer is an alloy and/or mixtureof silver, which has an index of refraction at 500 nm of approximately0.2, and tin.

In another non-limiting embodiment of the invention, the absorbing layercomprises nickel, stainless steel, chrome, molybdenum, tungsten,iridium, steel, iron, cobalt, cobalt as well as mixtures and alloysthereof.

In yet another non-limiting embodiment of the invention, the absorbinglayer comprises oxides, nitrides, and carbides. For example, theabsorbing layer can comprise one or more materials selected from oxides,nitrides and carbides of copper, manganese, titanium, iron, and chrome,as well as mixtures and alloys thereof.

According to the present invention, the absorbing layer(s) can bedeposited using any of the standard techniques discussed above inrelation to the infrared reflective layer. Other well known depositiontechniques such as plasma spray, arc spray, casting, etc. can also beutilized with the present invention.

The absorbing layer(s) can have any thickness. In a non-limitingembodiment, the thickness of each absorbing layer can range from 20 Å to300 Å, for example from 50 Å to 250 Å.

In addition to the coating composition discussed above, the presentinvention also encompasses a substrate coated with the describedcoating. According to the present invention, the coating described abovecan be deposited on a substrate. Suitable substrates include transparentmaterials such as, but not limited to, glass, ceramic, etc.

In a non-limiting embodiment of the invention, the substrate is glassmade via conventional float glass process. Suitable float processes aredescribed in U.S. Pat. Nos. 3,083,551; 3,220,816; and 3,843,346, whichare hereby incorporated by reference. In another non-limiting embodimentof the invention, the substrate is a glass float ribbon.

In many instances, it is desirable to place the absorbing layer as faraway as possible from a light source so the performance of any coatinglayers in the coating stack that have reflective properties will not becompromised. In a non-limiting embodiment, the present invention is acoating comprising an absorbing layer over a substrate; a firstdielectric layer over the absorbing layer; a first infrared reflectivelayer over the first dielectric layer; a first primer layer over thefirst infrared reflective layer; and a second dielectric layer over thefirst primer layer. The described coating configuration from the “firstinfrared reflective layer” to the “second dielectric layer” can berepeated any number of times to form a multi-layer coating over thesubstrate having one, two, three or more infrared reflective layers.

In another non-limiting embodiments the present invention is a coatingcomprising a first infrared reflective layer over a substrate; a firstprimer layer over the first infrared reflective layer; a firstdielectric layer over the first primer layer; and an absorbing layer.The described coating configuration from the “first infrared layer” tothe “first dielectric layer” can be repeated any number of times beforethe absorbing layer is included to form a multi-layer coating over thesubstrate having one, two, three or more infrared reflective layers.

In a non-limiting embodiment, the coating, when applied to a 0.16 inch(4.1 mm) thick clear glass substrate, exhibits a visible lighttransmittance equal to or less than 70%, for example, equal to or lessthan 50%, or equal to or less than 40 %, or equal to or less than 20%.As used herein, the term “clear glass” means a 0.16 inch thick glasssubstrate that exhibits a visible light transmittance of greater than90%. The coating, when applied to a 0.16 inch thick clear glasssubstrate can also exhibit a luminance (L* as measured according theC.I.E. 1931 standard with illuminant D65 and a 10° observer) equal to orless than 52, for example, equal to or less than 40, or equal to or lessthan 30.

Although not required in the present invention, a protective overcoat asis well known in the art can be the last coating layer in the coatingstack. In one non-limiting embodiment, the protective overcoat can be amixture of alumina and silica as described in U.S. patent applicationSer. No. 10/007,382 filed on Oct. 22, 2001, which is hereby incorporatedby reference. The protective overcoat can also serve as a barrier layerto certain materials, e.g. oxygen.

Various performance properties of the coated substrate such as reflectedcolor, transmitted color, etc. can be manipulated by varying thethicknesses of the respective coating layers in the coating stack. Oneof the major benefits of the coating of the present invention is itsability to exhibit a variety of reflected colors on both sides of asubstrate. Since the coating of the invention absorbs in the visiblespectrum and reduces the reflectance of the coating, the respectivesides of the coated substrate can exhibit different colors.

The coated substrate of the present invention can be used in numerousautomotive and architectural applications. For example, the coatedsubstrate can be used as a sunroof in a car or truck. The coatedsubstrate can also be used in residential homes and commercialbuildings.

In a non-limiting embodiment, the coated substrate of the invention isincorporated in an insulating glass (IG) unit, as is well known in theart. The IG unit can include a first glass substrate spaced from asecond glass substrate by a spacer assembly. The substrates are held inplace by a sealant system to form a chamber between the two glasssubstrates, as is well known in the art. Examples of suitable IG unitsare disclosed in U.S. Pat. Nos. 4,193,236; 4,464,874; 5,088,258; and5,106,663, which are hereby incorporated by reference.

A coated substrate according to the present invention can be utilized asthe first and/or the second glass substrate in an IG unit. In anon-limiting embodiment, the coated substrate of the present inventionis the first substrate, and the coating is on the surface facing thesecond glass substrate.

The present invention also encompasses a method for making the coatedsubstrate described above. The method can comprise depositing aninfrared reflecting layer over a substrate; depositing a primer layerover the infrared reflective layer; depositing a dielectric layer overthe primer layer; and depositing an absorbing layer over the primerlayer. In non-limiting alternative embodiments, the absorbing layer canbe deposited at different locations in the coating stack.

The present invention also encompasses a method for forming an absorbentlayer in a coated substrate after the coating has been deposited. Morespecifically, in a non-limiting embodiment, the method comprisesdepositing a first dielectric layer; depositing a first infraredreflective layer over the first dielectric layer; depositing a firstprimer layer over the first infrared reflective layer; depositing asecond dielectric layer comprising a material having a ΔG°_(f) ofgreater to or equal than −100 at 1,000° K. over the first primer layer;depositing a second infrared reflective layer over the second dielectriclayer; depositing a second primer over the second infrared reflectivelayer; depositing a protective overcoat which can serve as a barrier tooxygen over the infrared reflective layer; and heating the coating suchthat the metal ions in the second dielectric layer diffuse throughoutthe second infrared reflecting layer. The infrared reflective layer thatcontains the diffused metal ions after the heating step becomes theabsorbing layer of the invention.

Depending on the amount of diffused metal ions in the absorbing layer,the infrared absorbing properties of the absorbing layer will bereduced. Generally, the more metal ions in the absorbing layer, the lessreflective the layer is of infrared radiation. As a result, it ispossible to manipulate the absorbance and reflectance properties of theabsorbing layer by controlling the amount of metal ions that diffuseinto the absorbing layer.

In order to manipulate the amount of metal ions from the dielectriclayer, for example tin ions from a tin containing dielectric layer, thatdiffuse into the infrared reflective layer and convert it into theabsorbing layer during heating, a blocking layer can be depositedbetween the dielectric layer which supplies the metal ions and theinfrared reflective layer into which the metal ions diffuse. In anon-limiting embodiment, the blocking layer comprises a metal oxidelayer having a thickness sufficient to inhibit the diffusion of metalions into the infrared reflective layer. In a non-limiting embodiment ofthe invention, the blocking layer is selected from oxides of titanium,aluminum, zirconium, zinc and hafnium. The blocking layer can be anythickness. Typically, the blocking layer has a thickness of up to 60 Å,for example, up to 40 Å, for example, up to 20 Å.

EXAMPLES

The following non-limiting examples are included to illustrate thepresent invention.

Four examples were made. In the examples, the absorbing layer was notdeposited, but rather was formed from the migration of tin ions in thezinc stannate dielectric layer into the first infrared reflective layeras discussed below.

The examples were made in the following manner. A first dielectric layercomprising a first film of zinc stannate and an overlying film of zincoxide was deposited by MSVD on a 0.16 inch thick, clear glass substrate.The thickness of zinc stannate film of the first dielectric layer was276 Å, and the thickness of the zinc oxide film was 160 Å.

A first infrared reflective layer of silver was deposited at a thicknessof 118 Å over the first dielectric layer. A first primer layer oftitanium was deposited over the first silver layer at a thickness of 30Å. A second dielectric layer comprising a 130 Å thick film of zinc oxideand a 470 Å thick film of zinc stannate was deposited over the firstprimer layer. A second infrared reflective layer of silver having athickness of 119 Å was deposited over the second dielectric layer. Asecond primer layer of titanium having a thickness of 27 Å was depositedover the second primer layer. A third dielectric layer comprising a 130Å thick film of zinc oxide, a 483 Å thick film of zinc stannate and a130 Å thick film of zinc oxide was deposited over the second primerlayer. An overcoat layer comprised of 40% alumina and 60% silica wasdeposited at a thickness of 30 Å over the third dielectric layer.

A blocking layer comprising titania (TiO₂) was deposited at varyingthicknesses over the second dielectric layer (between the seconddielectric layer and a second silver layer). For Ex. 1, the thickness ofthe blocking layer was 20 Å. For Ex. 2, the thickness of the layer was40 Å. And, for Ex. 3, the thickness of the layer was 60 Å.

The coated substrates were then heated subjected to standard temperingconditions. It is believed that during the heating process, the zincstannate in the second dielectric layer was reduced and the tin ions inthe zinc stannate layer became mobile and diffused into the secondsilver. The diffusion of tin ions imparted absorbance properties intothe silver layer and led to the formation of the absorbing layer of theinvention. As discussed earlier, the blocking layer reduces the amountof tin ions that diffuse into the infrared reflective layer.

Various terms are used to characterize the performance properties ofglass substrates according to the present invention. A description ofthe terms appears below.

Luminous transmittance (LTA) was measured using C.I.E. 1931 standardilluminant “A” over the wavelength range 380 to 780 nm at 10 nanometerintervals in accordance with ASTM 308E-90.

Solar ultraviolet reflectance (SUVR) is the amount of ultraviolet energyreflected from a surface and was measured over the wavelength range from300 nm to 400 nm at 5 nm intervals.

Solar infrared reflectance (SIRR) is the amount of infrared energyreflected from a surface and was measured over the wavelength range from800 nm to 2100 nm at 50 nm intervals.

Total solar energy transmittance (TSET) is the total amount of solarenergy transmitted through a substrate and was computed using Parry Moonair mass 2.0 solar data based on measured transmittances from 300 nm to2100 nm at 50 nm intervals.

SUVR, SIRR and TSET were computed using Parry Moon air mass 2.0 solardata based on measured transmittances.

The L*, a*, b* values were based on CIE standard illuminant D65 and 10°observer.

The performance properties of the coated glass substrates according tothe present invention are shown in Table 1 below. In the table, “R1” ora “R2” appears before selected measured properties. The “R1” refers tothe measured property as being viewed from the coated side of thesubstrate. The “R2” refers to the measured property as being viewed fromthe uncoated side of the substrate.

TABLE 1 Performance Properties of a Coated Substrate According to thePresent Invention Example 1 Example 2 Example 3 Lta [%] 31.31 46.6360.40 R1SUVR [%] 10.49 8.41 8.18 R2SUVR [%] 5.13 5.12 5.14 R1SIRR [%]28.06 50.72 53.20 R2SIRR [%] 12.86 13.16 20.94 TSET [%] 20.05 27.6133.83 R1-L* 48.89 36.39 37.83 R2-L* 45.18 43.67 42.56 R1-a* −9.13 15.810.44 R2-a* −9.39 −6.61 −10.85 R1-b* −7.78 −3.95 −4.59 R2-b* −4.10 3.81−0.39

As seen in Table 1, a coated substrate according to the presentinvention at a thickness of 0.16 inches can exhibit the followingcombination of performance properties. Generally, the thicker theblocking layer, the less metal ions get diffused into the infraredreflective layer and the higher the Lta and the higher the SIRR (i.e,the less effective a silver layer is as an absorbing layer, the betterit is as an infrared reflecting layer).

For a substrate having a coating that initially includes two layers ofsilver, one of which gets subsequently converted into an absorbinglayer: the Lta can range from 30% to 65%, for example 33% to 61%; theR1-L* can range from 35 to 50, for example, from 37 to 48; and the R2-L*can range from 41 to 47, for example, from 42 to 45.

Additional solar properties such as reflection of UV energy, reflectionof IR energy and transmission of total solar energy were also recorded.For the coated side of Examples 1-3, the R1SVR ranged from 7% to 12%,for example, from 8% to 11% and the R1SIRR ranged from 28% to 55%, forexample, from 30% to 53%. For the uncoated side of Examples 1-3, theR2SUVR ranged from 4% to 6%, for example, from 4.5% to 5.5% and theR2SIRR ranged from 12% to 21%, for example, from 13% to 18%.

It will be readily appreciated by those skilled in the art thatmodifications may be made to the invention without departing from theconcepts disclosed in the foregoing description. Such modifications areto be considered as included within the scope of the invention.Accordingly, the particular embodiments described in detail hereinaboveare illustrative only and are not limiting as to the scope of theinvention, which is to be given the full breadth of the appended claimsand any and all equivalents thereof.

1. A coating comprising: a. an infrared reflective layer; b. a primerlayer over the infrared reflective layer; c. a dielectric layer over theprimer layer; and d. an absorbing layer; wherein the absorbing layer canbe either under the infrared reflective layer or over the dielectriclayer; wherein the absorbing layer comprises an alloy and/or mixture of(a) a metal having an index of refraction at 500 nm less than or equalto 1.0 and (b) a material having a ΔG°_(f) of greater than or equal to−100 at 1,000°K; and wherein the metal is silver and the material istin.
 2. The coating according to claim 1, wherein the absorbing layer isdeposited using a method selected from CVD spray pyrolysis, and MSVD. 3.The coating according to claim 1, wherein the absorbing layer has athickness ranging from 20 Åto 300 Å.
 4. The coating according to claim1, wherein the dielectric layer comprises a material selected from metaloxides, oxides of metal alloys, nitrides, oxynitrides, and mixturesthereof.
 5. The coating according to claim 4, wherein the dielectriclayer comprises a metal oxide selected from an oxide of titanium,hafnium, zirconium, niobium, zinc, bismuth lead, indium, tin, andmixtures thereof.
 6. The coating according to claim 4, wherein thedielectric layer comprises a zinc/tin alloy oxide ranging from 10 wt. %to 90 wt. % zinc and 90 wt. % to 10 wt. % tin.
 7. The coating accordingto claim 1, wherein the infrared reflective layer comprises a materialselected from silver, gold and copper.
 8. The coating according to claim1 deposited on a 0.16 inch thick clear glass substrate wherein thesubstrate exhibits an Lta of less than or equal to 50% and an L* ofequal to or less than 52 from at least one side of the substrate.